A new correlation has been discovered in optical observations of gamma ray bursts (GRBs) that may be the key to using GRBs as cosmological distance indicators, adding another rung to the so-called "distance ladder" that helps astronomers determine the size of the observable Universe.

Standard candles are objects with fixed luminosities that can be calculated by taking advantage of well-established relationships between an object’s luminosity and its physical properties—relationships that are independent of the object’s distance. Such objects enable the calculation of accurate astronomical distances. The furthest well-established standard candles to date are Type Ia supernovae, but GRBs have been observed at much greater distances (up to 13.2 billion light years vs. 11 billion light years for Type Ia supernovae). Thus, GRBs could provide accurate distances to events that happened only a few hundred millions years after the Big Bang, very close to when stars began to form in the Universe.